Marie Johnson, 42, who taught math at Granada High School, entered her plea on April 16.

Johnson was scheduled to be sentenced Wednesday but Alameda County Superior Court Judge Joseph Hurley instead sent her to Chowchilla State Prison for 90 days to determine whether it would be appropriate for her to be placed in prison for a longer sentence.

Johnson is scheduled to return to court on Aug. 13, when Hurley will determine where she will be placed.

Johnson initially was charged with 24 felony counts but an amended complaint reduced that total to nine counts.

She was placed on administrative leave after she was arrested at the school on Jan. 11, 2012, and resigned earlier this year during her dismissal process, school officials said.

When police interviewed Johnson after she was arrested she admitted to having sex with the male student, according to a probable cause statement by Livermore police Detective Joseph Draghi.

The charges to which Johnson pleaded no contest include unlawful sexual intercourse with a minor under the age of 16, oral copulation of a person under 16 and performing lewd acts on a child.

Draghi said the victim told a high school coach on Jan. 10, 2012, that he was a victim of “repeated molestation” and provided a detailed statement about “a long term sexual relationship with Johnson.”

Livermore police spokesman Steve Goard said authorities believe that Johnson began having sex with the boy shortly after he finished taking a class from her in December 2010 and sexually assaulted the boy 24 times over a six-month period.

Police believe the alleged sexual assaults occurred in Johnson’s car and in other undisclosed locations in Livermore, according to Goard.

Investigators believe Johnson and the boy formed their relationship through text messages, social networking on Facebook and instant messaging on a smartphone application called “Words with Friends,” Goard said.